The invention relates to a tool for bending a flat lead and a combined lead with small S-shaped curves, belonging to the technical field of transformer tooling equipment. The tool comprises a hydraulic pump (1), an oil cylinder (2), an outer connecting plate (3), a positioning plate (4), an inner connecting plate (5), a moving plate (6) and a fixing plate (7), wherein the hydraulic pump is connected with the oil cylinder, and the oil cylinder is provided with an inner connecting thread and an outer connecting thread; the outer connecting plate is connected with the outer thread of the oil cylinder and connected with the positioning plate through a bolt; the inner connecting plate is connected with the inner thread of the oil cylinder and connected with the moving plate through a bolt; the fixing plate is connected together with the positioning plate and the outer connecting plate through bolts; a flat lead and a combined lead (8) are placed in spaces among the fixing plate, the positioning plate and the moving plate; and the hydraulic pump is started, the oil cylinder acts, and the moving plate moves, thus the S-shaped curves of the flat lead and the combined lead are formed. The invention has the advantages that a special tool is used for bending the flat lead and the combined lead with the small S-shaped curves, and the length of the S-shaped curves of the leads least reach 50mm; and the tool has the characteristics of simple structure, convenient operation and time and labor saving and is beneficial to improving the quality of a transformer coil.